The present invention relates to elastomer seals and, in particular, to a pipe seals cast into concrete bulkheads, including septic tanks and manhole bases.
A common problem which occurs during underground construction is that of having to provide a watertight seal between a pipe member at the point of entry to a bulkhead. Such a problem can occur at septic tanks, manhole bases or varieties of other plumbing or electrical junction boxes.
Numerous styles and types of seals have been developed to resolve this difficulty. Many of such seals provide for a wedge fitting of the seal to the bulkhead. That is, a conical seal is fit about the pipe, before or after being inserted into the bulkhead. Sealing occurs with the driving of the tapered seal into the port.
Other seals known to applicant are formed undersized and include mechanisms to expand the seal walls, once inserted into an opening. Still other seals have been developed which can be cast directly into the bulkhead wall and which expand and contract about the pipe as it is inserted through the seal.
The present invention is directed to a seal of the latter type, which particularly finds application in concrete septic tanks or manhole bases. The inside diameter of such seals can range between a matter of a few inches to several feet, depending upon the outside wall diameter of the pipe.
To the extent applicant is aware of cast seals, the seals are typically supported on a mandrel and positioned approximately midway between form walls which define the bulkhead wall. Most commonly, a split or two piece mandrel is used having two mating cupped halves which restrain the seal. A separate restraint mechanism secures the mandrel to the bulkhead and seals the ends of the mandrel between the form walls. The mandrel may also pass through aligned holes formed into the casting form. Alternatively, the mandrel may be assembled and secured to a reinforcement wireform assembly which is cast as part of the bulkhead and prior to positioning the casting forms about the wireform.
Another assembly of which applicant is aware provides a cylindrical mandrel which supports a cylindrical seal between a pair of end retainers. The mandrel is positionable relative to the form via a slotted mandrel corepiece. A fastener extends through a slot in the corepiece to secure the mandrel to a form wall. The form walls otherwise abut the end retainers.
Although the foregoing devices provide adequate sealing, the mandrels are rather elaborate in construction. Depending on the number and sizes of pipe openings which must be formed, rather significant expenses can be incurred in forms alone. Setup time to form each sealed port can also be significant. To offset these expenses, Applicant has developed an inexpensive plastic mandrel which supports a seal in compressed relation between the casting form walls and such that a radially projecting flange is set into the poured concrete bulkhead.